<?php

/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Validate
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: UpcA.php 16223 2009-06-21 20:04:53Z thomas $
 */


/**
 * @see Zend_Validate_Abstract
 */
require_once 'Zend/Validate/Abstract.php';


/**
 * @category   Zend
 * @package    Zend_Validate
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_Validate_Barcode_UpcA extends Zend_Validate_Abstract
{
	/**
	 * Validation failure message key for when the value is
	 * an invalid barcode
	 */
	const INVALID = 'invalid';

	/**
	 * Validation failure message key for when the value is
	 * not 12 characters long
	 */
	const INVALID_LENGTH = 'invalidLength';

	/**
	 * Validation failure message template definitions
	 *
	 * @var array
	 */
	protected $_messageTemplates = array(
	self::INVALID        => "'%value%' is an invalid UPC-A barcode",
	self::INVALID_LENGTH => "'%value%' should be 12 characters",
	);

	/**
	 * Defined by Zend_Validate_Interface
	 *
	 * Returns true if and only if $value contains a valid barcode
	 *
	 * @param  string $value
	 * @return boolean
	 */
	public function isValid($value)
	{
		if (!is_string($value)) {
			$this->_error(self::INVALID);
			return false;
		}

		$this->_setValue($value);
		if (strlen($value) !== 12) {
			$this->_error(self::INVALID_LENGTH);
			return false;
		}

		$barcode = substr($value, 0, -1);
		$oddSum  = 0;
		$evenSum = 0;

		for ($i = 0; $i < 11; $i++) {
			if ($i % 2 === 0) {
				$oddSum += $barcode[$i] * 3;
			} elseif ($i % 2 === 1) {
				$evenSum += $barcode[$i];
			}
		}

		$calculation = ($oddSum + $evenSum) % 10;
		$checksum    = ($calculation === 0) ? 0 : 10 - $calculation;

		if ($value[11] != $checksum) {
			$this->_error(self::INVALID);
			return false;
		}

		return true;
	}
}
